Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
Inter-Department Program of Biomedical Sciences, Faculty of Graduate School, Chulalongkorn University, Bangkok, Thailand.
Am J Trop Med Hyg. 2018 Oct;99(4):987-994. doi: 10.4269/ajtmh.18-0401.
Mutations in the chloroquine resistance transporter gene of () are associated with drug susceptibility status of chloroquine and other antimalarials that interfere with heme detoxification process including artemisinin. We aim to investigate whether an increase in duration of artemisinin combination therapy (ACT) in Thailand could affect mutations in . The complete coding sequences of and dihydrofolate reductase (), and size polymorphisms of the merozoite surface proteins-1 and 2 ( and ) of 189 isolates collected during 1991 and 2016 were analyzed. In total, 12 novel amino acid substitutions and 13 novel PfCRT haplotypes were identified. The most prevalent haplotype belonged to the Dd2 sequence and no wild type was found. A significant positive correlation between the frequency of mutants and the year of sample collection was observed during nationwide ACT implementation ( = 0.780; = 0.038). The number of haplotypes and nucleotide diversity of isolates collected during 3-day ACT (2009-2016) significantly outnumbered those collected before this treatment regimen. Positive Darwinian selection occurred in the transmembrane domains only among isolates collected during 3-day ACT but not among those collected before this period. No remarkable change was observed in the molecular indices for other loci analyzed when similar comparisons were performed. An increase in the duration of artesunate in combination therapy in Thailand could exert selective pressure on the locus, resulting in emergence of novel variants. The impact of these novel haplotypes on antimalarial susceptibilities requires further study.
疟原虫氯喹耐药转运蛋白基因中的突变与氯喹和其他抗疟药物的敏感性状态相关，这些药物干扰血红素解毒过程，包括青蒿素。我们旨在研究泰国青蒿素联合疗法（ACT）持续时间的增加是否会影响疟原虫氯喹耐药转运蛋白基因的突变。分析了 1991 年和 2016 年期间收集的 189 株疟原虫的完整编码序列和二氢叶酸还原酶（），以及裂殖子表面蛋白-1 和 2（和）的大小多态性。总共鉴定出 12 种新的氨基酸取代和 13 种新的疟原虫氯喹耐药转运蛋白基因单倍型。最常见的单倍型属于 Dd2 序列，未发现野生型。在全国范围内实施 ACT 期间，观察到突变体的频率与样本采集年份之间存在显著的正相关（=0.780；=0.038）。在为期 3 天的 ACT（2009-2016 年）期间采集的分离株的单倍型数量和核苷酸多样性明显多于该治疗方案之前采集的分离株。仅在为期 3 天的 ACT 期间采集的分离株中，跨膜结构域发生了正向达尔文选择，而在该时期之前采集的分离株中则没有。当进行类似的比较时，分析的其他基因座的分子指数没有观察到明显变化。泰国青蒿素联合疗法持续时间的增加可能对 基因座施加选择压力，导致新变体的出现。这些新单倍型对抗疟药物敏感性的影响需要进一步研究。
